Yes it is one of the most famous DNS addresses, after google ( 8.8.8.8 )
The fact that avast online security detects something malicious doesn't make sense since it's not a website so this address doesn't use Hypertext Transfer Protocol (port 80, 443 , ...) , but a DNS protocol (port 53).
I wonder what AOS can see in it that is malicious..... even to see something in it
On the other hand , AOS is not a firewall but a subjective tool for website analysis and it is well known when AOS sees a new site (lack of reputation), it warms, that's what must happen here ?
What about 1.1.1.1 or 9.9.9.9 with AOS?